1961 Italian GP trophy

Going on the theme of trophies, the trophy pictured here is a real beauty. It was awarded to Alastair King for finishing 2^nd on a Joe Potts Manx in the 500cc class at the 1961 Italian GP held at Monza.  It is quite incredible that Alastair on a bike from a funeral parlour in Glasgow could go to one of the greatest races in the world and get a result like that!

The Lambretta Cup

There was a good contingent from Bellshill at Monza for the Italian GP. Joe had gone along to see how both Bob Mac and Alastair got on. Pim Fleming and his wife Jessie had treated it as a ‘busman’s holiday’ and had driven all the way from Bellshill!

For the meeting both Bob and Alastair has Works Bianchi’s for the 350cc class. For the 250cc race Bob also had a Honda 4. In the 500cc class the pair would be riding the Potts Manxes.

Alastair King and Bob McIntyre

The 350cc race was a disappointment for ‘Scotland’s terrible twosome’, as once again both Bianchi’s broke down. Things got worse in the 250cc class, as Bob crashed his Honda due to a split oil pipe putting oil onto his rear tyre. In the crash Bob suffered a broken collarbone, which put him out of the 500cc race.

It was therefore up to Alastair King to do the business in the Senior class. Mike Hailwood and Gary Hocking on MV’s were expected to challenge for the victory. Behind them Alastair would have to battle with the ‘Continental Circus’ riders on Manx Norton’s, such as Paddy Driver, John Hartle and Bob Anderson. As expected, Hailwood and Hocking went into the lead on the MV’s. Behind them there was a real battle involving Alastair King, Paddy Driver and Bob Schneider. Alastair was able to pull clear of Paddy Driver to be running in third position. On the 30th lap Gary Hocking crashed his MV at the South Hairpin. This left victory to Mike Hailwood on the other MV, with Alastair King second on the Potts Manx and Paddy Driver third.

500cc GP at Monza. Alastair King (Potts Manx) leading Hocking and Hailwood on the MV's

After Alastair’s great success in the Senior race he was given £350 in prize money as well the Lambretta Cup (pictured here) for finishing second and the Dunlop Cup. Later in the evening Alastair discovered that the prize money had disappeared from his hotel room. He called in some support to help find it. Mike Hailwood, Paddy Driver, Joe Potts and Pim and Jessie Fleming were all on their hands and knees looking for the money inside the room and outside in the bushes below. Hailwood even ruined his pair of white trousers searching all over the ground for Alastair’s winnings. Unfortunately they were unable to find the money (it had been stolen). Sadly for Alastair, even after his great success, he had to borrow some money in order to get back to Glasgow.

DRM 200cc 3 cylinder

A 200cc racing motorcycle might sound unusual to some, but in Scotland and Ireland the 200cc class was a major racing category.

 The DRM 3 cylinder 200cc machine was a bike put together in 1976 by Davy Mitchell (DRM) to promote his motorcycle shop in Kirkcaldy. At this time Davy was selling Fahron water cooled kits for 125cc Yamaha twins. Davy had the idea of producing a three cylinder machine for the 200cc racing class using the 125cc twin as a basis. Yamaha themselves had made a 350cc 3 cylinder for Katayama and there were other home brewed 3 cylinder 'specials’ such as Tony Dawson's Scitsu and Ted Broad's machine.

 The base for the DRM was two Yamaha AS3 bottom ends. The crankshaft was made by Hugh Ward by assembling three pairs AS3 flywheels. Instead of the normal 180 degree firing order used in the twin,  Hugh modified the cranks so they were 120 degrees apart. This modification allowed the use of a Femsa ignition from a 500cc Kawasaki triple.

 The crankcases and gearbox for the DRM came from the Yamaha AS3. Once again one and a half AS3 cases were utilised.  

The water cooled cylinders for the DRM were made by Fahron engineering. The 200cc 3 cylinder was based on one of their 125cc twin kits but with an extra cylinder added. The three cylinders were cast together as one unit and then iron liners were fitted. Each cylinder used a separate cylinder chamber head. Each of these heads was then covered by a single top which ensured sealing for the coolant.  

Two DRM three cylinder engines were made, but only one was ever completed. The completed engine was housed in a Jack Machin frame (one of two similar frames made by Jack for a 125cc). The tube diameter of the frame was ¾” (the other frame used a tube diameter of 7/8”). A steel fabricated swinging arm was made by Fahron engineering. A Ducati front end and Yamaha rear brake was fitted.

The DRM was only raced on a few occasions due to reliability issues (big-end failure on one occasion). However, the DRM did what it was meant to – cause a stir and promote Davy Mitchell’s shop.

Update. There are a few new links concerning the DRM. The first is an account from Mike Brown who helped with the machining of the crankcases on the DRM:

DRM account by Mike Brown

The DRM has also been restored by Hugh Ward. Pictures of the machine can be found in this post:

Restored DRM 3 cylinder

 

Charlie Bruce DOHC Velocette part 2

Charlie Bruce and his new DOHC Velo made their debut at the 1958 International Trophy meeting at Oulton Park. The 250cc race looked like it would be dominated by the NSU mounted quartet of Fron Purslow, Tommy Robb, L James and W Smith.  However Charlie and his new bike had other ideas and were able to break the NSU monopoly in the race and finish 4^th by ousting James.

Charlie Bruce remounted on his DOHC Velo after a crash (see the leathers)

Things didn’t go so well for Charlie at the 1958 Scottish Speed Championships being held at Beveridge Park.  Despite being a favourite for the 250cc class, Charlie crashed at the first corner in wet conditions. Charlie went on to record some good victories over the 1958 season at tracks like Crimond and Errol. Later in the season Charlie was back at Oulton Park for the Cheshire Championship meeting. Charlie finished 2^nd in his heat and 4^th in the final behind Dickie Dale, L James and K Terretta (all NSU mounted).

Squished cylinder head from the Bruce Velo

Even though the Bruce Velo was going well, Charlie, Joe and the team wanted to make it faster. The engine got the Potts treatment. A new crankshaft was made at Bellshill of 64mm stroke and a 70mm piston was machined from a forging that Joe had used on the Potts 250. The head was squished and the piston mated to suit, many years before Velocette decided to do the same. Charlie spent hours measuring and then replicating the NSU valve timing to use in his engine and acquired the nickname ‘Professor Chambers’ after the 4 figure log tables he used in the calculations required to machine the cams. When Charlie finally got all the cams made, Bob McIntyre presented him with a ‘medallion’ made from welding rods in the form of a Scottish thistle during a tea-break at Joe’s works!

The improved Bruce Velo went on to be even more successful winning the Scottish Championship in both 1959 and 1960 and became acknowledged as one of the fastest British 250cc machines.

Charlie Bruce on his DOHC Velo (taken from BP Racing Success' book)

The Joe Potts Trophy

I was recently looking through some old files when I came across something I wrote a few years ago for the first time the Joe Potts trophy was presented.

The Joe Potts trophy is presented annually at the Scottish Classic Racing Motorcycle Club’s Bob McIntyre memorial meeting. The trophy is awarded to the best performance by a rider over the weekend, who resides in Scotland. Along with the trophy the winner is given a bottle of Scotch Whisky, because as Bob McIntyre said regarding Jimmy Buchan’s double Manx GP victory in 1956 aboard Joe Potts Norton – “You can’t beat a double Scotch”.

The trophy is not only to remember Joe Potts but also the rest of the ‘Bellshill Beehive’ who worked with him.

The trophy consists of a titanium connecting rod, which was donated very kindly by Summerfield Engineering, mounted onto a Scottish granite base. The Granite base was donated by the Joe Potts funeral Parlour. The base is broadly machined into the shape of a coffin (remember Joe also ran a funeral parlour) and was polished by hand. In the big-end eye of the connecting rod there is an aluminium plug with the JP logo (from the JP cars made by Joe) machined into it. The little-end eye has another aluminium plug which has a Scottish thistle hand engraved onto it. The plate on the front of the trophy is also engraved in hand and says “The Joe Potts trophy, remembering the achievements of the Bellshill Beehive”. The engraving was done by the man who engraves the World Championship Snooker trophy.

Development of the QUB 250cc twin cylinder

It was in June 1967 that Gordon Blair, M Johnston and their associates at Queens University Belfast conceived a new type of inlet valve for a two-stroke engine. A 250cc water cooled twin cylinder engine with this rotary sleeve valve was designed and built from scratch and first road tested in 1969.

The rotary sleeve valve was described by Blair as a “disc valve translated into cylindrical terms”. See the following diagrams for details of the rotary sleeve valve. The valve (A) rotated on two bearings (D and E). Gas sealing between the cylinder, sleeve and the open ends is done by using labyrinth type seals (G). The running clearance between the stationary surfaces and the valve is 0.003”. The drive to the valve comes from a toothed rubber belt from the crankshaft (2:1 from the crank).

One advantage of this type of valve over a two-stroke disc valve engine is that the sleeve valve engine can be much narrower. A twin cylinder disc valve engine has a valve and carburettor on both ends of the crankshaft. Fitting of the primary drive to the gearbox and ignition system also becomes more difficult with a disc valve engine. For example the primary drive will come out between the two cylinders, making the whole engine package wider. The extra engine width limits chassis design and can have a negative effect on machine handling. The width of the QUB engine was 13”, which compares favourably to the 250cc units from Yamaha and MZ of the period (20” and 22” wide respectively).

The team at QUB did acknowledge some of the limitations involved with the use of their rotary sleeve valve. The first of these was that in order to obtain compact valve dimensions to achieve port timings of 40° abdc opening, 70° atdc closing, and approximately 50° from the fully closed to fully open position, the inlet port could not be a round hole, otherwise a valve with a diameter of 6” would be required! Instead a rectangular inlet tract was utilised with dimensions of 2.5” wide and 0.6” high in conjunction with a 2.5” diameter valve in order to achieve the required port timings. The addition of a conventional carburettor to the inlet port would produce a step change in section from round to rectangular, and have the associated large coefficient of discharge losses. Therefore the QUB team designed a “low pressure fuel injector with a barrel throttle valve”. Fuel was supplied from a varying section spindle set into G in the diagram. QUB also suggested that there would be a weight increase penalty of approximately 10 lbs due to the valve, inlet tract and fuel/air metering system.

Looking back with hindsight it can be seen that the inlet tract design has some other limitations. The use of the rotary valve means that the inlet tract is relatively long, which is less than desirable on a high performance engine. The inlet tract has also has a poor pathway into the crankcases. The port follows a ‘blind path’ to a wall before being expected to turn down into the cases.

For the port plan shown in the diagram QUB used an exhaust port timing of 201° and transfer port timing of 142°. These timings were for a designed 120 lbf/in² bmep at 11,000RPM resulting in a power output of 50 bhp.

The cylinder head of the engine ensured the squish area covered 50% of the piston area, at a clearence of 0.020”. The trapped compression ratio of the engine was 7.6:1, whilst the actual compression ratio was 15:1. The engine was water cooled and two separate cylinder heads cast out of RR50 and sealed by a single aluminium cover with an O-ring.  

A Hepolite piston with a single dykes ring was used in the QUB 250cc. The single L-shaped piston ring was made from nodular iron. A 12mm gudgeon pin was utilised with an INA roller bearing in the connecting rod little end. The pistons run in cast iron liners with a 0.006” clearance. The liners are shrunk into the alloy water jacket and then honed to size with a surface roughness of 12-15µin c.l.a. The bore was 57mm and the stroke is48mm, giving a bore/stroke ratio of 1.19.

The steel I section connecting rod had the small and big end eyes nitride to a depth of 0.010” to Rockwell 60c for the needle roller bearings. The big end was a 'Durkopp' cage from Ransome, Hoffman, Pollard, SK 22 x28 x 13 FV.  

The original crankshaft for the engine had the crankpins and mainshafts held in with Loctite, as opposed to being pressed together. For alignment a jig was used to hold the crankshaft assembly whilst the joining compound set. During early service, chattering was noticed at the crankpins. The crank design was then modified to incorporate interference fits for the crankpins. The crankpins were pressed into position with an interference of 0.0035-0.004”. The mainshaft joint was retained as a Loctite joint. Double row needle roller main bearings were used, with a ball bearing on the timing side to stop end float. The crankcases split horizontally.

The water pump is driven by a rubber belt at 3.5:1 from the rotary valve (7:1 from the crankshaft). And has a flow rate of 10 gal/min. A thermostat controlled the block temperature to 88°C. An oil pump was driven off the water pump which delivers oil to the intake tract on top of the big end bearings. Castrol R40 oil was used and also mixed in the fuel to make a petroil mix of 25:1. A Lucas transistorized ignition system was used.

The engine was coupled to a 5 sped Albion gearbox via a Morse “Hy-Vo” chain and mounted in a frame made by Colin Seeley. The total weight of the machine was 265lbs.

The engine was run up on a Heenan and Froude DPXO dynamometer. The ignition timing was optimised at 11,000 RPM and found to be 21.5-22°BTDC. There was a very steep rise in power from the engine from 9,000 RPM and a sudden cut-off at 11,250 RPM. Peak power was found to be 45 BHP, but it was expected that with some development 10% more would be achieved.

In 1969 the machine was raced on two occasions, but it broke down due to small end bearing failures. The best performance on these occasions was a 92 mph of the Ulster GP circuit at Dundrod.